class Student(object):
    count = 0
    def __init__(self, name):
        self.name = name
        Student.count += 1

s1 = Student('wangming')
print(s1.count)

s2 = Student('wangxi')
print(s2.count)

s3 = Student('wuyun')
print(s3.count)

print(s1.count)

print(getattr(s2,'name'))
setattr(s2,'name','wwanyiyi')
print(getattr(s2,'name'))